1. Field of the Invention
The present invention relates to a substrate processing apparatus having a step of processing a substrate and a method for manufacturing a semiconductor device.
2. Description of the Related Art
Conventionally, as one step of manufacturing processes for a semiconductor device, for example, such as DRAM, a substrate processing step for forming a thin film on a substrate has been carried out. Such substrate processing step has been carried out by a substrate processing apparatus which includes: a processing chamber for storing and processing substrates stacked in multiple stages in horizontal posture; a processing gas supply nozzle for supplying a processing gas to the inside of the processing chamber; and an exhaust line for exhausting the inside of the processing chamber. Next, substrate processing step loads a substrate holder which supports a plurality of substrates to the inside of the processing chamber, and supplying the gas from the processing gas supply nozzle to the inside of the processing chamber while exhausting the inside of the processing chamber by means of the exhaust line, whereby the gas is caused to pass spaces between each of the substrates and thus a thin film is formed on each of the substrates.
However, in the above-described substrate processing step, the gas is difficult to flow to the vicinity of each of the substrates. This causes difference in gas supply amount between to the vicinity of the outer periphery and to the vicinity of the center of each substrate, and accordingly the in-plane uniformity of substrate processing sometimes deteriorates. For example, there are some cases where a thin film formed in the vicinity of the outer periphery of the substrate is thicker compared with a thin film formed in the vicinity of the center of the substrate.
In order to promote supply of the gas to the vicinity of the center of each substrate, a method can be conceived in which ring-shaped straightening vanes are provided, each straightening vane being between the circumferential edge of each substrate supported by the substrate holder and the inner wall of the processing chamber. However, in such a method, there are some cases where a substrate transfer mechanism for transferring the substrates to the substrate holder interferes (gets contact) with the straightening vane. In the case where a large stacking pitch of the substrates is given to avoid such interference, there are some cases where the number of substrates which can be collectively processed is reduced. In addition, the substrate holder which has ring-shaped straightening vanes is easy to break and is expensive because of complexity of the structure thereof.
As described above, in the above-described substrate processing step, the gas is difficult to flow to the vicinity of each substrate. This causes difference in gas supply amount between to the vicinity of the outer periphery and to the vicinity of the center of each substrate, and accordingly, the in-plane uniformity of substrate processing sometimes deteriorates. For example, in the case of an Hf oxide film (HfO film) formed by supplying an amine-based Hf raw material gas and an O3 gas onto a substrate, a Zr oxide film (ZrO film) formed by supplying an amine-based Zr raw material gas and an O3 gas onto a substrate, and the like, there are some cases where a film formed in the vicinity of the outer periphery of the substrate is thinner compared with a film formed in the vicinity of the center of the substrate.
In order to promote supply of the gas to spaces between adjacent substrates, a method can also be conceived in which ring-shaped straightening vanes are provided, each straightening vane being between the circumferential edge of each substrate supported by the substrate holder and the inner wall of the processing chamber. FIG. 4 is a schematic structural view of a substrate holder which has such straightening vanes. By providing ring-shaped straightening vanes such that they surround the circumferential edge of the substrates, a part of the processing gas can be adhered onto each straightening vane, whereby, a film formed in the vicinity of the outer periphery of each substrate can be made thinner. Note that, FIG. 5 is a schematic structural view of a substrate holder which does not have straightening vanes.
However, in such a method, there are some cases where a substrate transfer mechanism for carrying the substrates to the substrate holder interferes (gets contact) with the straightening vanes. In the case where a large stacking pitch of the substrates is given to avoid such interference, there are some cases where the number of substrates which can be collectively processed is reduced, whereby productivity of the substrate processing deteriorates. In addition, the substrate holder provided with ring-shaped straightening vanes is easy to break and is expensive because of complexity of the structure thereof.
Hence, the investors and the like made an intensive study on a method of promoting supply of gases to the vicinity of the center of each substrate without reducing the number of substrates which can be collectively processed. As a result of this, the investors have found the knowledge that supply of the gas to the vicinity of the center of each substrate can be promoted and the supply amounts of the gas to the vicinity of the outer periphery and to the vicinity of the center of each substrate can be made more uniform, by supplying an inactive gas from both sides of a processing gas at the same time when supplying the processing gas to the inside of the processing chamber. The present invention has been made on the basis of such knowledge obtained by the investors and the like.